Modern aircraft are furnished with a flight management system which provides a flight plan consisting of points of transit, connected together. At each point of transit, up to the destination airport, the flight management system provides predictions: time of transit, speed, altitude, fuel remaining on board. Moreover, the flight management system proposes an optimization of the flight plan: optimal cruising altitude, optimal speed for each phase of flight.
It is known that a civil flight plan followed for example by a civil transport airplane comprises a departure airport and a destination airport, plus possibly a diversion airport. In civil aviation, the load carried on board the aircraft (passengers, freight) does not vary in the course of one and the same flight. Moreover, the variations in the weight of fuel are due to the consumption of the engines and are therefore forecastable throughout the flight.
On the other hand, a tactical flight plan, that is to say a flight plan intended for a tactical flight, must take account of tactical events liable to modify the predictions. More precisely, for an aircraft involved in a tactical flight, four types of tactical events may cause the load transported to vary, or cause the quantity of fuel on board to vary (other than by the normal consumption of fuel), in the course of the flight:                a decrease in the load transported, upon an aerial drop or an unloading during a tactical step which corresponds to a landing on an intermediate field for tactical purposes (standby, loading, unloading, etc.), followed by a takeoff toward the destination, or toward another tactical step;        an increase in the load transported, upon loading during a tactical step;        a decrease in the fuel on board (not due to the aircraft's own consumption), upon in-flight refueling in the guise of tanker aircraft; and        an increase in the fuel on board, upon in-flight refueling in the guise of refueled aircraft.        
The standard flight management systems take no account of these tactical events in the predictions of the flight plan before these events have actually occurred. Likewise, there is no optimization of the flight plan beyond the point at which a tactical event will take place, before this event has actually taken place.
When a tactical event has actually taken place, or has taken place partially (partial drop or refueling), the predictions are updated with the new parameters of the aircraft. Specifically, when the change has occurred, the aircraft weight parameters are modified by the crew so that the predictions are recalculated as a function of the current situation.
The standard flight management systems are therefore unable to produce a tactical flight plan, that is to say to produce during flight preparation a flight plan taking account of tactical events that will arise in the course of the flight.